A friend of mine wants to know if it is safe to cut a door out of an old diesel tank with a torch. it's ben emty for over 10 yrs, but he still has qualms about cutting it.would it be better if he just left it alone? Thanks David from No Dak

I have heard stories "wink, wink" about old heating oil tanks that were buried underground being cut open on top with a torch, filled with sand, and buried again. Bear in mind though that this may be illegal in your area. The sniffer wells required and hazmat disposal costs of contaminated soil from a leaky tank can cost a large fortune to dispose of legally. Now if you could fill it with water to get rid of the fumes, and still have enough heat to cut it, you may have an idea.

Although I've never done this, I talked with a guy that works on gasoline tanks. To keep things "in order", he connects a hose to the exhaust pipe of his truck, the other end in the tank. Letting the truck run for a while, and during his work, he can weld or cut on the tank without any "mishaps". No oxygen, no boom.

CO2 works just the same. Tank is not much money and you have some pressure. It's still a risk. I don't know any "absolutely" safe ways to cut open an old fuel tank.
If it ever had gas in it, I wouldn't touch it.

Add a few inches of water and a few pounds of dry ice. Lower an oxygen detector into the tank and when the oxygen levels are down to nothing, start cutting, if the detector detects any oxygen (say a breeze blows some in), stop and wait until the levels drop again before cutting. Any cutting can generate sparks, air chisels, torches sawzalls, what is important is to keep the inside of the tank oxygen free. Also it's best not to stand near the ends of the tank - if it was to go, the ends blow off and out (so they tell me, I've never seen it happen)

We've cut underground gas tanks in half for disposal using both the torch and sawzall that sill had heavy fumes.

If you just go cut on it with a torch without doing anything else you stand a pretty fair chance of getting killed. Probably better than 70 percent. Filling the tank with water works ok but you need it full. People that do it all the time always use a device called an explosivometer or "sniffer" as some call it. The heat of the torch can bring out vapor from old tanks that you couldn't smell before you started so you need to check it for fumes often. A cleaned tank that tests safe will almost always show bad if it is left in the hot sun for a few hours. Steam cleaning the inside will get it back in the safe region and then a few hours of hot sun has it back in the explosive range. You have to get it clean and then get in and out right away. I know people who actually weld on the inside of leaking gasoline trucks to fix cracks but they keep their methods of cleanup a trade secret. If I had that job to do I would hire someone; I love life to much to save money on something like that or try some off the wall method.

All the above is very true for gasoline tanks. As for diesel, I have welded on diesel vehicle tanks without purging them, and all they do is smoke out the vent if there is some fuel left inside. Diesel fumes are not as explosive as gasoline. Diesel is hard to ignite.

HOWEVER - Don't take this to mean that I said it's OK to cut the tank without purging it! I don't know for a fact that nothing can happen from the diesel fumes, and besides, there can be something more volatile mixed in with it.

Hi guys:
thanks for all the input!! as for filling it with water.... woooooooooeeeeeeeee lots of water!! the tank is over 10,000 allons!!long time filling! forest, dont have a saws all with a bi metal blade(not even a bi metal blade on the farm) maby its time to get one tho.what if it was cut in the winter? it gets down to -50'F here.exaust fumes, sounds like a good idea. David from No Dak

Here in Nova Scotia the most common heating fuel is Furnace oil which is simply Diesel fuel by another name without the highway taxes. ( it comes from the same tank at the bulk plant) Due to envirormental concerns homeowners are now required to replace there heating oil storage tanks every 10 years. Needless to say this leeds to a large number of tanks being removed and to dispose of them it is required that they be wiped down on the inside to remove oil residue. To do this the tanks are cut in half and the most common method is a gas powered friction saw and the second most common method is a recip saw. The tanks are simply drained and then cut I am not aware of anyone ever bothering to purge a tank or remove the oxygen.I have witnessed many tanks cut with a friction saw which of course produces lots of sparks and I have never seen or heard of one of these tanks exploding. This of course applies to diesel fuel and gasoline would be a very diffrent situation where a great deal of prcaution would be required

Several years ago I was in charge of a small shop. We had a 300 gallon diesel tank that was leaking. The guys that worked for me wanted to weld it. It was only diesel and they knew how to do it. There was a shop about a mile from us that did a lot of work on tanks. I told them not to weld the tank take it to the XYZ shop as they did this kind of welding all the time. One of my guys took the tank to the XYZ shop in the back of a pickup truck. “What do you need” “We need this diesel tank welded “ ”Back it in here” The young fellow working there hooked the ground to the tank and struck an ark. That was the last think he ever did. After spending many days in court I learned a few things about welding tanks. It is or was the law that you can weld on fuel tanks after they have been purged with live steam for 24 hours. The truck that delivered the diesel had pumped gasolene at its last stop. There was about one quart of gasoline in 100 gallons of diesel. After the fuel was drained from the tank there was still gasoline fumes in the tank. Water, dry ice, car exhaust may work but the law is live steam for 24 hours. You never know if there are few drops of gasoline or what ever in that diesel tank. It only takes a few drops and you are dead.

You don't need any gasoline in a diesel tank to cause an explosion. If the tank is warmed to the flash point of diesel, about 100 degrees F, it reacts just like gasoline. This temperature is easily obtained or exceeded if the tank is sitting in the sun and a dark color. As a firefighter we deal with fuel spills on asphalt quite often and treat them with great respect for the same reason. Hot roads and diesel fuel are a catastrophe waiting to happen.

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